For 1 thing, Concord grapes, high in pectin, require heating for decent pressing, and the juice comes out of the press hot, and possibly hot enough to qualify as mevushal. Because there is no good way to measure the temperature of distinct particulates like grapes except 1 at a time, but juice can be subjected to turbulence to mix, then in-line recording thermometers can accurately measure the temperature of the flowing liquid. But the flash detente, on the other hand, while it raises the temperature of the intact grape (presumably it can be set to greater than 185 degrees F), the liquid comes out cool.

Isaac Chavel wrote:And I thought, from the discussions last spring/summer, that their (Hagafen & Herzog) secret was flash-heating before pasteurization. My memory faulty?

Isaac

Isaac, Did you mean before bottling? Indeed Herzog, Hagafen, and others do flash-heat their wines early on, after fermentation, but well before malolactic fermentation (if not filtered away). Essentially, they flash the liquid as soon as the wine becomes wine. The poorer wines are flashed at bottling, as the desire there is to keep some wines unflashed (like in Israel), where almost all the wine sold there now has stopped being flashed (unless it is made for Badatz), but the wines sold for export are flashed. So they flash it as bottling, which is the WORST TIME possible to flash a wine.

Just a reminder that very few hashgachos accept 180 degrees F. Rav Moshe Feinstein allowed much lower, on the order of 175 or even less, but major hashgachos in the USA accept no less, lechatchila, than 185, and in Israel the standard may be about 191 (which is also the standard of the Tzelemer Rav, lechatchila, I seem to recall). And in the USA, most white wines undergo bishul (in the form of HTST Processing) at the must stage, whereas reds must wait because the plate heat exchangers do not allow particulates, such as skins and seeds, the way tube-in-shell heat exchangers do, but the plate exchangers are far more efficient.